Search found 6 matches

by JavaBean
Wed Aug 25, 2010 6:50 am UTC
Forum: Computer Science
Topic: Ackermann Function
Replies: 7
Views: 2810

Re: Ackermann Function

C++, and noticeably faster then the naive implementation. Dynamic programming FTW! (defn ack [x y] (cond (= x 0) (inc y) (= y 0) (ack (dec x) 1) :else (ack (dec x) (ack x (dec y))))) Clojure: a little less verbose than C++. And if you want to cache results, just: (def ack* (memoize ack)) edit: spac...
by JavaBean
Wed Jun 02, 2010 6:50 pm UTC
Forum: Coding
Topic: Manufactoria - Make Turing Machines with Conveyor Belts
Replies: 350
Views: 119247

Re: Manufactoria - Make Turing Machines with Conveyor Belts

That works only if the three blues are all in a row; your solution rejects [BBRB]. If it were as simple as your 5-part solution, you wouldn't be the first to notice.
by JavaBean
Wed May 26, 2010 3:06 pm UTC
Forum: Coding
Topic: Manufactoria - Make Turing Machines with Conveyor Belts
Replies: 350
Views: 119247

Re: Manufactoria - Make Turing Machines with Conveyor Belts

My robo-children answer is n 2 too, and with a slightly larger constant factor than yours. As Berengal demonstrated, though, it doesn't have to be - his looks n*log(n) to me, with a pretty small constant factor? Most of the time it's O(n), even, but for pathological inputs like RRRRRRRRRRRRBBBBBBBBB...
by JavaBean
Tue May 25, 2010 10:34 pm UTC
Forum: Coding
Topic: Manufactoria - Make Turing Machines with Conveyor Belts
Replies: 350
Views: 119247

Re: Manufactoria - Make Turing Machines with Conveyor Belts

I'm surprised everyone is having so much trouble with Rocket Planes - that wasn't the one that tripped me up. The general approach I used was Rather than move blues to the front, move reds to the back A more detailed (still pseudo-code) algorithm: ⋅ Copy/skip any number of blues ⋅&nbs...
by JavaBean
Fri Feb 29, 2008 11:17 pm UTC
Forum: Coding
Topic: Using regexec in C/C++
Replies: 5
Views: 3864

Re: Using regexec in C/C++

int regexec(const regex_t *preg, const char *string, size_t nmatch, regmatch_t pmatch[], int eflags) from reading the docs on regex.h, this is what i gather: i believe nmatch is the number of matches you want and pmatch is an array that needs to be of size nmatch. after running regexec, pmatch will...
by JavaBean
Fri Dec 15, 2006 9:30 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0099: "Binary Heart"
Replies: 28
Views: 30060

Capital/lowercase Os

When I looked at the questions about the capital O versus lowercase o, I noticed that there are exactly 4 repetitions of the string, and thus 8 Os, some of which are lowercase and some uppercase. That's 8 sources of data, each capable of encoding a single bit - surely, there must be a super-secret m...

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